This invention relates generally to the field of swimming and diving, and more particularly to an ergonomic swim fin apparatus based on the locomotion methods and strategies used by the most efficient fish. This invention can be assembled to various levels of complexity, to be used to swim at varying degrees of effectiveness and purpose. Much work has been done in recent years in biomimetics to study efficient swimming fish to try to effect a man-made free moving aquatic device that- approaches their propulsion, efficiency, acceleration and maneuverability. Universities such as MIT, Northeastern University, the University of Tokai, Japan, the Herriot-Watt University, Edinburgh, Scotland, Texas A&M University and Aeroprobe Corp., and the University of New Mexico and Artificial Muscles Research Institute are all researching various aspects of this propulsion system, as described in U.S. Pat. No. 6,138,604 and other publications. Scientific analyses developed from free swimming fish and robotic models of fish have been directed towards the development of a pelagic free swimming aquatic vehicle. In the instant invention, applicable principles that parallel these biomimetic studies have been adapted to create a swim fin apparatus that is created for ergonomic human swimming, underwater or at the surface, that will imitate fish and their propulsion, efficiency, acceleration and maneuverability. This swim fin apparatus also allows the swimmer to adapt to various swimming conditions and swimming goals by allowing certain elements of the apparatus to be selectively interchanged to meet these goals. This apparatus also provides an elegant solution for non-swimming problems associated with the general use of swim fins, such as: walking with the swim fins, an easy method for manufacture of said swim fins, and solutions for sore tendons produced by swimming with past swim fms.
A few attempts, most notably U.S. Pat. Nos. 2,423,571; 2,950,487; 4,934,971 and 5,906,525; have attempted to deal with the fish propulsion problem by focusing on moving a portion of a swim fin which has been shaped like a fish or dolphin tail fin or a variation or such. Simply moving a tail fin through the water (without a flow of water over a “lifting” surface at a correct angle of attack) produces a flopping form with little or no propulsion. At best, the tail fin in this system acts like a webbed foot, with its associated problems.
U.S. Pat. No. 2,099,973 comes close to adapting the propulsion system of efficient fish type propulsion, but has several inherent problems. First, it employs an upper stiff paddle that has no shaped foot pocket and does not let the toes flex. This would be uncomfortable to use when swimming or walking, because the toes would continually be constricted and under substantial pressure. Second, the lack of a formed foot pocket would cause pressure points on of the top of the user's foot. Third, the flat stiff paddle does nothing to enhance or channel the flow of water over the fin to enhance propulsion. Finally, this patent doesn't include a tail fin that gives “lift” to the propulsion system for increased power and efficiency, as is found with fish propulsion systems.
U.S. Pat. No. 6,375,531 granted to the present inventor comes the closest to adapting the system used by fish for propulsion. It uses a stiff flat blade for propulsion, a flexible portion, and a“wing shaped” tail to provide lift. It is a very effective form of locomotion that fulfills all of the requirements for effective fish propulsion system, but it is not as ergonomic in its design with regard to the human foot and anatomy, as is the present invention. The invention described in U.S. Pat. No. 6,375,531 uses a stiff blade that extends beyond the toes which creates unnecessary work and undue pressures on the foot of the swimmer, and makes walking in the fins very difficult. Secondly, the invention described in U.S. Pat. No. 6,375,531 requires more material in the production of the swim fin than required by a swim fin disclosed in the present invention, because the swim fin described in the latter-noted patent must be longer and heavier than the present embodiment shown in FIG. 1, 5, 11, 12 and 15, to produce similar propulsion results.
The vast majority of prior art swim fins have functioned as webbed feet or paddles. Webbed feet and paddles work to push water, but not as efficiently as the propulsion system used by fish. Two clear problems with webbed feet and paddles are that water isn't pushed effectively, and a recovery stroke is required to arrive at a position to properly push on each stroke of the swim fins (a substantial waste of energy and a cause of drag.)
The numbers of patents using the “webbed foot” or “paddle” form of propulsion are too numerous to mention. A selected number of them are mentioned because of their historical importance or superficial resemblance to the instant invention. Each of these prior art patents, simply increase the surface area for pushing water, and they include:
U.S. Pat. No. 74,931, issued in 1868, which the earliest known patent in this art, in which the webbed foot concept is extremely clear, with elongated forms of the toes and fingers which are webbed with cloth.
U.S. Pat. No. 169,396, issued in 1875, is a series of hinged flaps and other forms positioned above the surface of the foot.
U.S. Pat. No. 281,005, issued in 1883, utilizes hinged flaps connected to the bottom of a shoe form.
U.S. Pat. No. 335,015, issued in 1886, is an ingenious system of retractable flaps positioned at the sides and front of the foot.
U.S. Pat. No. 636,364, issued in 1899, is a form of swim fin worn with a shoe that would balloon out in the backward kick to increase the surface area.
U.S. Pat. No. 1,113,820, issued in 1914, disclosed hinged flaps positioned above a shoe.
U.S. Pat. No. 1,187,963, issued in 1916, disclosed hinged flaps above and to the sides of a shoe.
U.S. Pat. No. 1,374,077, issued in 1921, disclosed swim fins having a single flat surface supported above the shoe that did not move.
U.S. Pat. No. 1,571,462, issued in 1926, disclosed swim fins having an increased surface area, with a wire form on the sides and front of the foot that incorporated a cloth spread under the foot to encompass the wire form.
U.S. Pat. No. 1,729,477, issued in 1929, discloses swim fins with wire forms and cloth, to create a larger form above the shoe.
U.S. Pat. No. 1,788,013, issued in 1931, professes to “provide a device similar in form to the webfoot of a water bird”, with a web form attached to the bottom of a bathing shoe.
U.S. Pat. No. 1,911,828, issued in 1933, attaches two hinged fin forms horizontal to the floor to a shoe to create moveable swim fin flaps.
U.S. Pat. No. 2,277,538, issued in 1942, employs swim fins having two hinged flaps attached to a shoe that meet at the top of the shoe.
U.S. Pat. No. 2,672,629, issued in 1954, traps water by a system of wire supports and cloth webbing that surrounds the sides and front of the foot. A small amount of flexibility is provided in the toe portion of the wire supports and webbing.
U.S. Pat. No. 5,795,204, issued in 1998, extends the area of swimming shoes by providing a semi-flexible swim fin flap extending from the bottom of the shoe to the outside side of the foot, which does not extend beyond the toes of the shoe.
Other swim fin designs have tackled design problems along with the problem of propulsion. These patents are representative of many others, dealing with common problems in manufacturing or common usage of the swim fins. U.S. Pat. No. 3,315,286 describes a swim fin that has a hinged swimming blade that enables the swimmer to walk easily while wearing the swim fins. Other known swim fin swivel systems have been developed to aid walking. U.S. Pat. No. 5,597,336 describes a swim fin with an open instep instead of a closed foot pocket, which discloses a simple two piece mold, for use in swim fin production. U.S. Pat. No. 5,975,973 employs an asymmetrical swim fin design that promotes a small amount of rotation while swimming to decrease tendon soreness due to swimming with swim fins.